PHOTOPLETHYSMOGRAPHY DEVICE AND METHOD

• US 20130131475A1
• Filed: 10/16/2012
• Published: 05/23/2013
• Est. Priority Date: 07/30/2009
• Status: Active Grant

• Current Assignee: Oxitone Medical Ltd.
• Original Assignee: Oxitone Medical Ltd.
• Inventors: Eisen, Leon, Kamisnky, Alexander, Fine, Ilya
• Granted Patent: US 8,868,149 B2
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/7285 for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal A61B6/5205, A61B6/541, A61B8/5207, A61B8/543 take precedence

Abstract

A system and method for measuring one or more light-absorption related blood analyte concentration parameters of a mammalian subject, is disclosed. In some embodiments, the system comprises: a) a photoplethysmography (PPG) device configured to effect a PPG measurement by illuminating skin of the subject with at least two distinct wavelengths of light and determining relative absorbance at each of the wavelengths; b) a dynamic light scattering measurement (DLS) device configured to effect a DLS measurement of the subject to rheologically measure a pulse parameter of the subject; and c) electronic circuitry configured to: i) temporally correlating the results of the PPG and DLS measurements; and ii) accordance with the temporal correlation between the PPG and DLS measurements, assessing value(s) of the one or more light-absorption related blood analyte concentration parameter(s).

Claims

1. A method of measuring one or more light-absorption related blood analyte concentration parameters of a mammalian subject, the method comprising:

a) effecting a photoplethysmography (PPG) measurement of the subject by illuminating skin of the subject with at least two distinct wavelengths of light and determining relative absorbance at each of the wavelengths;

b) effecting a dynamic light scattering measurement (DLS) of the subject to rheologically measure a pulse parameter of the subject;

c) temporally correlating the results of the PPG and DLS measurements; and

d) in accordance with the temporal correlation between the PPG and DLS measurements, assessing value(s) of the one or more light-absorption related blood analyte concentration parameter(s).

2. The method of claim 1 wherein the blood analyte concentration parameter is selected from the group consisting of a blood oxihemoglobin concentration parameter, a blood carboxyhemoglobin concentration parameter and an arteriovenous oxygen difference (AV difference) parameter.

3. The method of claim 1 wherein temporal correlating and/or value assessing includes:

i) determining from the measurement of step (b) a description of a pulse timing; and

ii) in accordance with the DLS pulse-timing determining, associating each PPG measurement of a plurality of measurements with a different respective pulse-relative time value describing a pulse-relative temporal position of the PPG measurement within the pulse; and

iii) determining the light-absorption related blood analyte concentration parameter in accordance with pulse-relative temporal positions.

4. The method of claim 2 wherein the pulse-relative temporal position describes at least one of:

i) a time elapsed between the occurrence of a pulse event and the subsequent measurement time of PPG data; and

ii) a time elapsed between the measurement time of PPG data and an occurrence of a subsequent pulse event.

5. The method of claim 4 wherein the pulse event is selected from the group consisting of an initiation of the systolic phase, a peak of the systolic phase, an initiation of the diastolic phase, and a zero-crossing of a time derivative of a pulse value.

6. The method of claim 1 wherein the DLS is single scattering DLS and/or single wavelength DLS.

7. The method of claim 1 wherein the DLS measurement and the PPG measurements are local to each other.

8. The method of claim 1 wherein step (d) includes:

i) computing a parameter descriptive of the temporal correlation between measurements of step (b) and step (c); and

ii) in accordance with the computed temporal correlation parameter, determining a time-dependent PPG data quality value associated with each PPG measurement; and

iii) computing the light-absorption related blood analyte concentration parameter(s) by assigning greater weight to PPG data having a higher data quality value and lesser or no weight to PPG data having a higher data quality value.

9. A method of measuring one or more light-absorption related blood analyte concentration parameters of a mammalian subject, the method comprising:

a) effecting a photoplethysmography (PPG) measurement of the subject by illuminating skin of the subject with at least two distinct wavelengths of light and determining relative absorbance at each of the wavelengths;

b) effecting a non-PPG rheological pulse measurement to rheologically measure a pulse parameter of the subject;

c) temporally correlating the results of the PPG and rheological measurements; and

d) in accordance with the temporal correlation between the PPG and rheological pulse measurements, assessing value(s) of the one or more light-absorption related blood analyte concentration parameter(s).

10. The method of claim 9 wherein the effecting of the non-PPG rheological pulse measurement includes effecting at least one of:

a) a speckle analysis;

b) a measurement of a blood shear stress;

c) a light interference measurement;

d) a acoustic or optical Doppler measurement; and

e) an electrical impedance measurement.

11. The method of claim 9 wherein the blood analyte concentration parameter is selected from the group consisting of a blood oxihemoglobin concentration parameter, a blood carboxyhemoglobin concentration parameter and an arteriovenous oxygen difference (AV difference) parameter.

12. A method of measuring blood parameters of a mammalian subject, the method comprising:

a) effecting a photoplethysmography (PPG) measurement of the subject by illuminating skin of the subject with at least two distinct wavelengths of light and determining relative absorbance at each of the wavelengths;

b) effecting a dynamic light scattering measurement (DLS) of the subject to rheologically measure a pulse parameter of the subject;

c) temporally correlating the results of the PPG and DLS measurements; and

d) in accordance with the temporal correlation between the PPG and DLS measurements, assessing a venal contribution and/or relative contributions of arterial and venal blood to one or more light-absorption related blood analyte concentration parameter(s).

13-15. -15. (canceled)